1. Field of the Invention
The present invention relates to a side-knock type mechanical pencil in which a lead feeding mechanism is disposed in an inside portion of a barrel and a knock button is disposed in a side portion of the barrel so that the knock button can be pressed inward in a radial direction of the barrel, and the knock button is pressed to move the lead feeding mechanism back and forth, thereby feeding a lead from the barrel.
2. Background Art
Japanese Utility Model Laid-Open No. 55-171577/1980 is known as one example of a side-knock type mechanical pencil. This publication describes a head and a side-knock type mechanical pencil in which an internal tube provided with a mouth ring at its lower end and shorter than an external barrel is movably accommodated in the external barrel; an internal mechanism return spring and engaging means for projecting the mouth ring from the lower end of the external barrel and retracting the mouth ring into the external barrel are provided in the external barrel; an external hole is provided in proximity to a gripping index of the external barrel; an internal hole is provided in the portion of the internal tube which corresponds to the external hole; a lead case, a joint pipe and a three-split chuck are integrally accommodated in the internal tube; a fastener is provided inside the mouth ring and outside the three-split chuck which projects from the internal tube; a slider which causes the three-split chuck to move in the internal tube toward a lead point and is restored by a spring is provided in the internal tube; a side-knock button which can press downward the inclined surface of the upper end of the slider is provided in the external hole; and a knock cover which can press the three-split chuck toward the lead point is provided at the upper end of the lead case.
In operation, one lead is separated from the leads stored in the lead case by the upper end of the joint pipe and is then introduced into the three-split chuck through the joint pipe. The slider and the three-split chuck move forward by the radial pressure of the side-knock button, so that the lead gripped by the three-split chuck is fed forward.
In general, if the side-knock type mechanical pencil is made to carry out a lead feeding operation, i.e., if the side-knock button is pressed, the forces act on the slider not only in the forward direction thereof but also in the direction in which the side-knock button is pressed. The force which acts on the slider in the latter direction becomes a force which inclines the slider, and this force increases as the side-knock button is pressed. The inclination of the slider bends the connection portion between the joint pipe and the three-split chuck. At this time, a failure occurs in the feeding of the lead, i.e., the lead is caught by the bending so that it becomes unable to be fed in the forward direction or in a sufficient amount.
In recent years, consumers have increasingly preferred inexpensive products. It has increasingly necessary to decrease the costs of products because of higher labor costs. Writing tools, such as ball-point pens and mechanical pencils, are not exceptions, and the above-described side-knock type mechanical pencil has been forced to be inexpensively manufactured. To inexpensively manufacture the side-knock type mechanical pencil, there are a number of available methods, such as formation of two parts as one integral part, adoption of a simplified assembling method, or a reduction in the number of parts. However, the formation of two parts as one integral part makes it possible to inexpensively manufacture parts themselves, but may need a complicated and expensive forming mold in order to form a product of particular shape. For this reason, a reduction in the number of parts may be adopted. If the number of parts is reduced, the assembly becomes simple.
However, if the number of parts is simply reduced, the required functions will be lost. For example, in the case of the above-described example, if the lead case and the joint pipe are omitted, a lead may exceed the slider and enter a spring portion, so that the lead may not be gripped by the three-split chuck and may become unable to be fed forward. In addition, when the side-knock button is pressed, a lead may be broken.